System for preparing packed columns and coated capillary tubes useful in gas chromatography

ABSTRACT

An integral system contained in a suitable housing which includes means for coating particulate support material with stationary phase chemicals, means for draining liquid from the coated support material, means for drying the coated support material, and means for transferring the dried, coated support material into a gas-chromatography column. Means for cleaning and coating capillary tubes is also disclosed. Additionally means for conditioning packed columns and capillary tubes is disclosed.

United States Patent 1191 11] 3,831,555 Srinivas Au 27 1974 SYSTEM FORPREPARING PACKED 3,213,412 113/1322 i lg beimm 23/259 y 3,26 ,33 1 g gCAPILLAR 3,270,784 9/1966 CHROMATOGRAPHY 3,425,811 2/1969 Carignan23/292 P NIS [76] Inventor: Srivas Rangachar Srinivas, 2850 FOREIGN ATEOR APPLICATIONS Webb Ave, APL SJ, Bronx N Y' 360,601 10/1922 Germany34/76 10468 Primary Examiner-Morris Kaplam Flledi 7, 1972 Attorney,Agent, or Firm-Rocco S. Barrese [21] Appl. No.: 232,583

57 ABSTRACT [52 vs. C] 118/506 34/36 118/48 An integral System in asuitable housing 118/73 which includes means for coating particulatesupport 51 1m. (:1. (3236 13/08 material with Stationary Phase chemicalsmeans for [58] Field Of Search 118/48 49 429 303 58 draining liquid fromthe Coated Support material 118/63 72 7 77 means for drying the coatedsupport material, and 209/155 158 5 71 23/259 means for transferring thedried, coated support material into a gas-chromatography column. Meansfor [56] References Cited cleaning and coating capillary tubes is alsodisclosed. Additionally means for conditioning packed columns UNITEDSTATES PATENTS and capillary tubes is disclosed. 2,397,438 3/1946 Schmid23/292 x 3.193267 7/1965 Beck l1 Clam, 5 Drflwmg Figures PAIENIEB 182 1W 3. 88.1 .555 sum 10$ 3 PATENTEB 3.831.555

am 2 ar a FIG.

PATENTEDAHEZTIW I 3.831.555-

SIEH 3W 3 TO PYROMETER I67 F so so 525 so; PACKED COLUMNS il 57 540 5| E2s 02 KO 28 04 PACKED COLUMNS CAPILLARY OOLUMNS /\/\/\/v\/v 57 544 5 5EM CAPILLARY COLUMNS 5 6E FRITTED BASE\\ HEATING W ELEMENT L AC POWERSOURCE CONTROL FIG. 5

AC POWER SOURCE SYSTEM FOR PREPARING PACKED COLUMNS AND COATED CAPILLARYTUBES USEFUL IN GAS CHROMATOGRAPHY BACKGROUND OF THE INVENTION In theart of gas-liquid chromatography (GLC), it is necessary to preparepacked columns as well as coated capillary tubes which are employed inconjunction with a suitable detector instrument, gas chromatograph, forobtaining analytical data relative to chemical compositions of a highlycomplex organic substance e.g., essential oils, perfumes, flavors, etc.The preparation of a packed column involves firstly, coating a suitableparticulate packing support with a layer of stationary phase chemical,drying the coated support, and then transferring the coated and driedpacking into a column of desired dimension in a manner such that thepacking material is uniformly or homogeneously distributed throughoutthe column. The preparation of capillary tubes involves firstly,cleaning a tube with various solutions and then coating the wallsthereof with a layer of stationary phase chemical.

In the caseof gas-solid chromatography (GSC), the wide bore columns ofdesired dimension are packed with an inert solid support, such as,Chromosorb porous polymer beads.

Various packing supports and stationary phase chemicals are well knownin the gas chromatography art. Typical packing supports include inertmaterials such as diatomaceous earths, glass beads, polymer beads,crushed fire brick and the like. Stationary phase chemicals includepolyesters, polyethylene glycols, methyl and phenyl silicones,substituted silicones as well as many other chemicals.

Various techniques and devices are known in the prior art for performingindividual steps involved in the preparation of columns and capillarytubes. For example, U.S. Pat. No. 3,513,562 describes a fluidized dryingdevice for drying coated packing support materials. The use of capillarytubes coated with stationary phase materials is described in U.S. Pat.No. 2,900,478. Vibrating devices, for example, are known for the purposeof assisting in the uniform packing of gas chromatography (GC) columns.While the various prior methods and means are operable to produce packedcolumns and capillary tubes which may perform adequately for manyapplications, there has remained a need to maximize efficiency of theentire procedure for preparation of columns and capillary tubes suchthat the time and expense of preparing such means for use in gas-solidand gas-liquid chromatographic analyses might be substantially reduced.There has also remained prior to this invention a need for preparingpacked columns with a very large number of theoretical plates andcapillary tubes which will yield more highly consistent and reproducibleanalytical results.

It is important to properly condition the packed and capillary columnsbefore using them for analysis of the complex mixture of organiccompounds. In the prior art, while conditioning the columns, one end ofthe column is connected to the inlet of the carrier gas whereas theother end is left open to the atmosphere by not connecting it to thedetector inlet which otherwise would contaminate the detector system.Thus, in order to meet the aforementioned pre-requisite, very expensiveand highly sophisticated gas-chromatograph units are employed therebyincreasing the time and expense of preparing such columns forsatisfactory use in gas-solid and gas-liquid chromatography. Hence,there has been a great need for a column pre-conditioning means thatwould be more efficient, and economical to achieve this desired end.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the presentinvention a system is provided which is useful for the coating of theparticulate support material with stationary phase chemicals, drying orpreconditioning the coated support and transferring the prepared coatedsupport material into the GC column in an efficient and highlysatisfactory manner. The integrated means of the present invention isalso useful for cleaning and coating of capillary tubes employed in GLCanalysis as well as in packing the columns with porous polymer solidsupports such as Chromosorb polymer beads used in gas-solidchromatography.

The system comprises the following basic and essential elements.Firstly, a housing means is provided to maintain the means hereinafterrecited. The housing means will usually include a suitable face panelupon which the various valves, gauges, power switches, pyrometer andflow meters can be placed. The various conduit means, pumps, heater,:and other operating parts will preferably be enclosed within thehousing.

A first port means is provided which is connected to an extrinsiccoating and drying column or to a reservoir for cleaning and coatingcapillary tubes. The port means are preferably located in the side panelwalls of the housing means and the various extrinsic columns, tubes,flasks, etc. are removably connected to the ports but located outside ofthe housing. Vacuum means such as a conventional vacuum pump ispreferably provided in the housing for effecting the various draining,evacuating and transferring operations performed in the preparation ofgas chromatography columns and capillary tubes. The vacuum meanscommunicates with the port means through suitable conduit means.

Preferably, the vacuum means is connected to the port through anextrinsic trap flask which can be readily emptied and which is useful intrapping relatively expensive stationary phase chemicals when drainingexcess solution from a solid support coating operation.

A second port means communicates with the first port means through afirst conduit means which is equipped with flow control valves andheating means. When a source of inert gas, e.g., nitrogen gas cylinder,is connected to the second port means, the gas can be passed at adesired temperature and flow rate into the base of a suitable column todry coated packing or, alternatively, in a stripped-down embodiment ofthe system of the invention can be connected to a vessel em ployed forcleaning or coating capillary tubes to force solutions through suchcapillary tubes.

A second conduit means connected to an extrinsic packing column throughthird port means communicates with the nitrogen supply port to providemeans for transferring coated packing material from the packing columninto the gas-chromatography column to be packed.

The above-stated combination of means are capable of effecting thecoating, drying, packing of wide-bore columns as well as cleaning andcoating of capillary tubes in accordance with the system of the presentinvention. However, the preferred and enlarged system of the presentinvention is hereinafter described.-

It is apparent that the entire preparation of gaschromatography columnsand capillary tubes can be effected in accordance with the presentinvention with maximum efficiency and minimum handling time. Minimizinghandling of support material during the coating and drying operationresults in more reproducible, evenly coated and efficient coatedsupports. In line with this invention very fine particles are readilyeliminated and the particular size of the final coated product made morehomogeneous. OVerall, the columns prepared in accordance with thepresent invention are found to be superior in analytical performance tocolumns prepared by prior art methods.

The system of the present invention can also be employed to control thegas supply to a column conditioning unit, and is particularly useful inconjunction with the new column conditioning means hereinafterdescribed.

REFERENCE TO THE DRAWINGS FIG. 1 of the drawings illustratesdiagrammatically, in elevation, one preferred embodiment of the systemof the present invention.

FIG. 1A, like FIG. 4, illustrates the novel means useful for cleaningcapillary tubes in conjunction with the system of the present invention,as shown by FIG. 1.

FIG. 18 illustrates a smaller novel means useful for cleaning capillarytubes in conjunction with the system of the present invention, as shownin FIG. 1.

FIG. 2 illustrates a novel and preferred column reservoir useful inpreparation of coated packing supports.

DETAILED DESCRIPTION OF INVENTION The invention is hereinafter describedin detail with reference made to FIGS. 1 thru 5 of the drawings. Housing20 which can be made of metal, wood or plastic forms a container for thesystem hereinafter described. For example, a housing 30-inches high, 24-inches wide and IO-inches deep is suitable.

Port 1 serves as an inlet for nitrogen or other inert gas to conduit 2.Port 1 is preferably situated flush with the left side panel of housing20. Conduit 2 is made of any suitable metal, plastic or ceramicmaterial. For example, copper tubing one-eighth inch in diameter issatisfactory for all conduits. Valve SP is provided in conduit 2 tocontrol the flow of inert gas which, for example, can be provided by anitrogen cylinder. The control knob of valve SP is preferably situatedon the front panel surface of housing 20. Each item designated in thedrawing by F following the numeral is, likewise, situated on the frontpanel surface of housing 20. The ports such as l, 118, 123, 436 and 78are preferably situated flush with the left side panel of housing 20while ports 142, 43 and 58 are flush with the right side panel.

Nitrogen purifier 11, which is preferably equipped with replaceablecartridges, serves to eliminate moisture and oil from commercial gradenitrogen.

Union cross 15 joins conduit 2 to conduits 14, 471 and 3. Auxillaryvalve 19F is provided in conduit 3 to control the gas supply when dryingcoated support materials or when cleaning or coating capillary tubes.Auxillary valve 470 F in conduit 471 controls the gas supply to port 436which can be connected to the conditioning means, e.g. as shown in FIG.5.

Pressure gauge 152F is provided in conduit 3. This is intended primarilyfor use when coating and drying solid supports and packing wide-borecolumns and is preferably a 0-200 psi gauge. This gauge can also be usedfor cleaning or coating capillary tubes up to 200 psi. Gauge 152F shouldbe isolated from the high pressure system to prevent damage thereto byclosing valves 134F and 19F when 152F is not in use. Union cross 27renders conduit 4 in open communication with conduits 3 and 72.

Conduit 14 communicating between union cross 15 and port 142 is providedchiefly for use in cleaning capillary tubes when the pressure which isrequired exceeds about 200 psi. This line may be isolated where suchcleaning operation is not performed or eliminated by modification ofgauge 152F. Control valve 307F is situated in conduit 14. Pressure gaugel5lF is preferably graduated 0-400 psi. Conduit l4 communicates withconduit 3 thru tee 138. Tee 300 and valve 301F are provided foremergency pressure release when employing elevated pressures in conduit14 for cleaning or coating capillary tubes.

. Conduit 4 and control valve 31F are provided to supply nitrogen gas,e. g., for drying coated solid supports. Heating means 34 is provided incombination with pyrometer l67F interconnected by a thermocouple line 35in order to provide nitrogen gas heated to the desired temperature.Preferred heating means comprises an electrically heated aluminum blockaround which a stainless steel conduit is wound. In order to improveheat transfer the section of conduit wound around the aluminum block canbe reduced in diameter, e.g., from one-eighth inch to about 0.02- inch.A switch (not shown) can be provided on the front panel to regulate thetemperature of 34.

Union cross 39 provides a junction point among conduits 4, 6, l0 and 7.Conduit 6 and port 43 are provided, e.g., for coating and drying supportmaterial; and also for transferring cleaning solutions into thereservoir 192. Conduit 7, valve 54F and port 58 are provided as drainand evacuation means. Conduit 10, valve 127F and port 123 are providedfor use in loading the pack tube 96 with coated support material.

Vacuum pump which is connected to an electric power source and line 8which can be a heavy gauge flexible tubing or the like are preferablyprovided as part of the system for use in draining, loading, chargingreservoir 192 and evacuating operations. A switch (not shown) can beprovided on the front panel of the housing to actuate pump 70.

Conduit 12 which communicates between port 118 and gas-flow meter 122 isprovided, e.g., for use in conjunction with packing a gas-chromatographycolumn with Chromosorb polymer beads or with coated packing supportmaterial or for measuring the flow rate through the columns beingconditioned.

Conventional vibrator 221 is preferably attached to the side panel ofhousing for use in packing a gaschromatography column. A switch (notshown) can be provided on the front panel to actuate 221.

Adjustable clamps 116 and 119 can be provided attached to the top of thehousing 20 for the purpose of holding-in-place columns such as 50 and 96employed in the coating and packing procedures as hereinafter described.

FIG. 2 illustrates a reservoir assembly useful in coating and dryingsolid support materials. Glass tube 50, e.g., is heavy, borosilicateglass 24 inches high and 1 inch inside diameter. Female-threaded knurledaluminum ring 182 fits snugly around tube 50 and male threaded knurledaluminum ring 183 fits snugly around glass funnel 48. They are assembledby screwing the threads of 183 into 182. The base of tube 50 then holdswasher 186 snugly in place which, in turn, holds a removable, porousdisc 187 made'of sintered glass or any other suitable material firmlyagainst the lip of the glass funnel. Flexible hose 185 is connected tothe base of funnel 48 and valve 47, e.g., by means of screw clampsdisposed at each end thereof. Copper tubing 184 connects the reservoirassembly with port 43.

Coil 153 is a thin-walled stainless steel tubing (oneeighth inch O.D.)coiled and then flattened along the coil and adapted to be inserted intoglass tube 50 for use in drying the coated material. The upper end 1538is shaped as a hook to fit over the upper end of 50. Tile bottom part153A extends into the bottom portion of tube 50. The function of thisdevice is hereinafter described with reference to drying coated packingmaterial.

FIG. 3, illustrates a novel and preferred reservoir assembly for use intransferring coated or uncoated packing support material into awide-bore gas chromatography column. Elongated tube 96 made of heavy,borosil icate glass or other suitable material rated to withstand apressure of 200 psig is fitted at each end with femalethreaded knurledaluminum rings 93 and 97. Tube 96, e.g., is l8-inches high and l'inchinside diameter. A circular plate 103 having an outside diameter suchthat it fits snugly into the base of tube 96 is rigidly connected toelbow 105. Plate 103 is machined to provide a planoconcave surface whichaids in preventing the coated support material transferred into tube 96from being crushed and fragmented while packing GC-column 101. When malethreaded aluminum ring 102 engages 97, plate 103 is held snugly in placeand provides a base for the assembly.

Flat plate 90 having a bent tee 82 rigidly connected thereto is held inplace by engaging male-threaded knurled aluminum ring 92 with 93 thefemale threaded knurled aluminum ring.

FIG. 4 illustrates novel means useful, e.g., for cleaning and coatingcapillary tubes. Elongated thick-walled cylinder 192 capable ofwithstanding elevated pressures up to about 2,000 psi is adapted withthreaded ends 194 and 193. Conduit 205 having threads 203 and 204 cut ineach end thereof engages threads 193 at the bottom of the cylinder.Tee-shaped conduit 196 engages threads 194 at the top of the cylinderthrough threads 204. Dip tube 195 is removably secured to the top of 196at threads 198 by means of threads 206 out in nut 199 which is rotatablymounted on dip tube 195. Protruberances 201 and 200 restrain axialmovement of nut 199 on 195. Threads 202 are provided at the top of 195for making further connections to auxilliary means. The operation ofthis assembly is described with reference to procedure for cleaning andcoating capillary tubes. The dip tube 195 is designed to transfercorrosive cleaning liquids such as nitric and nitrous acids, ammoniumand sodium hydroxides, etc., into cylinder 192 with great care andwithout danger to the analyst or to objects in the laboratory workingarea. All fittings are designed to give pressure-tight operation atabout 1,500 psi. Cylinder 192 is made of stainless steel. Although acylinder of 150 to 500 cc capacity can be used, a cylinder of about 300cc capacity is preferred for cleaning capillary tubes. For coatingcapillary tubes a cylinder with 10 to cc capacity could be employed, buta cylinder with 50 cc capacity is most desirable for this purpose.

FIG. 5 illustrates novel means useful for conditioning the packed andcapillary columns. This device includes an oven that can be electricallyheated up to 500C and equipped with connections for suspending wide borepacked columns and capillary columns simultaneously in the oven. Meansare also provided to ascertain the packing density by measuring thecolumn back pressure at any chosen temperature during conditioning whichshould later enable the analyst to choose the optimum flow settings on aconventional gas chromatograph without going through the tedious andtime consuming procedure of flow rate calibration. Necessary fittingsfor connecting packed columns of one-eighth inch to one-half inchdiameter tubings up to 50 feet in length and capillary columns up to1,000 feet in length to the gas supply and to the flow measurementdevices are provided. The oven chamber is so designed that columns ofevery conceivable shape such as straight biwalled columns, hair pin orfolded hair pin, pan cake, helical or randomly coiled to 10 inches indiameter used in the gas chromatographic analyses of complex organicmixtures can be accomodated readily. Housing 500 which is preferablymade of metal forms a container for the system hereinafter described.For example, a thermally insulated steel housing 36 inches high,

24 inches wide and 12 inches deep is suitable from an.

economic. point of view. This will accomodate four packed wide borecolumns and two capillary columns each up to 50 feet and 1,000 feet inlength respectively.

Ports 540, 541, 542, 543, 544 and 545 serve as inlets for nitrogen orother inert gas to individual columns. Ports 501E, 502E, 503E, 504E,505E and 5065 serve as the outlet fittings for the exit end of thecolumns.

All ports, 540 to 545 and 50l-E "to 506 E are preferably situated flushwith the left side and right side panels of the housing 500.

The conditioning unit is connected to the unit contained in housing 20by connecting port 586 at the terminal part of conduit 521 to port 436.Union cross 522 connects pressure gauge 560, inlet conduit 521, andconduits 519 and 516. Gauge 560 is preferably graduated 0-200 psi andpermits measurement of the gas inlet pressure.

Conduit 519 is in communication with conduit 539 through valve 501 andflow controller 514.

Conduit 539 supplies inert gas to individual ports 540 thru 543. Valves501, 502, 503 and 504 are provided to control the gas supply toindividual columns connected to the ports 540, 541, 542 and 543,respectively.

Tees 570 through 573 situated at the positions indicated in FIG. 5connect the respective valves to the column inlet ports and are also incommunication with the rotary valve 508 through the correspondingconduits 525, 526, 527, and 528. Rotary valve 508 is a conventionalrotary valve, e.g., as made by RS. Crum Co., for connecting any one ofconduits 525 thru 530, to pres sure gauge 510.

Conduit 516 is in communication with conduit 524 which supplies inertgas to capillary columns connected to the ports 544. and 545 through therespective valve 505 and 506. A pressure regulator e.g., to 50 psi, witha gauge 509 and a control valve 507 is provided in conduit 524 toregulate the gas supply.

Tees 574 and 575 connecting respectively the valve 505 to port 544 and506 to 545 are in communication with the rotary valve 508 through therespective conduits 529 and 530.

Rotary valve, preferably a 7-way valve, is connected to a pressureguage, e.g., 0-200 psi, and is in communication with the inlet of thecolumns through the conduits 525 through 530. Choosing the appropriatepositions by means of a knob on the rotary valve enables the analyst toread the back pressure at the inlet of the column which is beingconditioned. By placing the knob to the vent position, pressure on thegauge can be released.

Thermocouple lead 590 can be connected to pyrometer 167F within housing20 to read the temperature of the oven.

Column outlets, 501E, through 506E can be connected to the flow meter122F on the housing 20 through conduit 111 and port 118. This enablesthe analyst to determine the flow rate through the column.

PROCEDURE FOR COATING AND DRYING SOLID SUPPORT MATERIAL Column reservoir50 is assembled as described with reference to FIG. 2 and is held inplace by clamp means 119. Conduit 184 is connected to port 43. Coil 153is removed during the coating procedure. All valves including valve 47should be closed. Any desired coating solution is introduced through theopen top into 50. A preweighed amount of particulate support material isthen introduced into the coating solution and permitted to standundisturbed for a suitable period of time, e.g., 5 minutes.

The following procedure is followed only in the case of solution coatingtechnique but omitted when a slurry coating method is used.

The top of tube 50 is preferably closed off once solid support materialis added by inserting in the upper part thereof a vertically elongatedtube containing a special mixture of oxysorb, ascarite and activatedcharcoal. This eliminates oxygen moisture, and organic vapors from airentering the system while draining the excess solution.

Drain flask 62 is connected to port 58 and line 8. Vacuum pump 70 isstarted and valves 54F and 47 are opened to permit draining of solutionfrom tube 50.

When solution is removed from tube 50 leaving wet coated solid material,hose 185 is disconnected from valve 47. The same solvent used fordissolving the stationary phase chemical can be introduced into valve47, with the vacuum system on, in order to dissolve any stationary phasematerial, which may be very expensive. The dissolved material is thentrapped in flask 62 from which it can be recovered for reuse.

Once the solid support material in tube 50 has been coated, thefollowing procedure is observed to dry the coated support. Pump isturned off and valve 54F is closed. Hose 185 is reconnected to valve 47and vertically elongated tube is removed from the top of 50. Coil 153which has been coated with oil or other sticky substance is insertedinto tube 50 such that 153A extends well below the surface of the coatedsupport material. Valves 31F and 19F are opened. Nitrogen supply isconnected to port 1 and the tank delivery gauge is set to 50 psi. ValveSE is opened slowly until the pressure reading on 152F is, e.g., betweenabout 10-20 psi. The nitrogen gas flows thru purifier 11 and thru heater34 for elevation in temperature to a desired level for drying thesupport material in tube 50. Coil 153A prevents the wet cake of coatedsupport material from rising as a mass during the initial drying period.Thereafter the flow of gas upwardly thru porous sintered disc 187, whichacts as a sparger or distributor, and the particulate solids tends tofluidize the material in tube 50. The finer particles tend to migrate tothe top of tube 50 due to electriation by the inert gas are trapped on153 and then discarded. Thus, the particulate support material is mademore homogeneous relative to particle size distribution during thedrying step in tube 50.

When the support material in tube 50 is dried and free flowing, electricpower supply to the heater is turned off and all valves are closed toshut off the gas supply. Tube 50 is disconnected at valve 47 and thecoated support material is transferred to a suitable airtight containerfor storage until the packing operation. Alternatively, it iscontemplated that tube 50 can be employed directly in place of thepacking reservoir 96, after assembling the appropriate parts describedwith reference to FIG. 3.

PROCEDURE FOR PACKING WIDE-BORE COLUMNS The assembled packing column 96,described with reference to FIG. 3 is held in place by clamp means 116.Line 85 is connected to tee 82 at 82A. The alternate opening 82B isconnected to gas supply port 78 by means of connecting line 83. Port 123is connected to elbow at the base of tube 96 by means of conduit 115.Special connector 108 is packed with stainless steel or glass wool toprevent the coated packing material from being drawn below that point.With all other valves closed, valves 127F and 54F are opened whilevacuum pump'70 is started and the precoated and dried support materialin the air-tight container 84 is held at the end of line 85. This drawsthe coated packing support material from container 84 into tube 96.

Once the desired amount of support material whether coated or uncoatedhas been transferred into 96 the following procedure is employed to packwidebore GC columns, e.g., one-eighth to three-fourth inch outerdiameter GC columns with the support material..Line 85 is disconnectedfrom 82" and the opening is-closed with a suitable plug. Line isdisconnected from 105.

The GC column 101 bent to the desired shape is brought into contact withvibrator 221. One end of this column is connected to 105, while theother end is connected to port 118 by means of conduit 111. Specialconnector 108 is used between the GC column end and the conduit 111. Thenitrogen supply is connected to port 1. By opening valves F and 19F thepressure reading on 152E is brought to about 100 psi, for example, whichis suitable for packing a column ft. long and one-eighth inch outerdiameter. The vibrator 221 is turned on. With valves 134F and 31Fclosed, valve 74F is opened causing packing support material to flowfrom tube 96 into the GC column 101. When the column is packed in auniform manner the pressure on 152F and the flow reading on 122F becomeconstant and stable. If there is an obstruction in the tube the flowreading on 122E will fall to zero and the pressure shown in 152E will behigher than expected. It is apparent that columns of constant dimensionpacked with the same coated support material will exhibit the same finalflow reading on 122F and pressure on 152E. Thus, the system of thisinvention permits preparation of highly reproducible and reliable packedcolumns.

When the gas chromatography column is packed, the vibrator 2211 andnitrogen valve 5F are turned off. When the pressure on 152E shows zerothe column may be disconnected, conditioned and then connected to aconventional GC detector.

PROCEDURE FOR CONDITIONING COLUMNS The following procedure is followedto condition the packed columns or coated capillary tubings.

In order to condition the columns or the capillary tubings, one endthereof, preferably, the detector end In order to obtain an appropriateflow of gas the knob on rotary valve 508 is set to the proper positionto read the column inlet pressure on gauge 510. The pressure reading ongauge 510 is then set to an appropriate reading at the proper selectedtemperature by adjustment of control valve 501, e.g., 40 psi for a 10feet by oneeighth inch packed column.

The column is conditioned at the temperature chosen for a period ofabout 2 to 24 hours for packed columns and capillary tubings and perhapsfor several days depending upon the purity and homogenity of liquidstationary phase or the inert solid support, such as, chromosorb porouspolymer beads and also depending upon whether the columns so preparedare intended for GC coupled MS analyses. For example, the column isconditioned at, 200C for 24 hours with gas flowing through the column.

During the column conditioning period the flow rate atthecolumnexitatany column temperature can be 1 is connected to any ofthe inlet ports 540 through 5431 conveniently measured by connecting thecolumn exit to the flow meter 122F through conduit 111 and port 118.Further measurement of the column back pressure at the carrier gas inletwhich bears a direct relationship to the flow through the column can bedc tected by means of gauges 510 or 509.

After the specified period of time, e.g., 24 hours, the oven is cooledto room temperature and the column temperature is reset, e.g., to C andthe pressure reading on gauge 510 is reset to 40 psi. The flow rate atthe column exit is measured by connection with 122E. For example, theflow rate is 30 c.c. per minute at 100C and 40 psi inlet pressure. Theconditioned column can now be removed and transferred to a GC unit. Ifthe inlet pressure is set to 40 psi at a column temperature of 100C, theflow rate of gas will automatically be 30cc per minute.

Important features and advantages of the column conditioning unitinclude the following:

1. Allows the analyst to determine the desired optimum flow ratecalibration during the conditioning operation;

2. Abbrogrates contamination of components separated by gaschromatography thus more reliable and accurate spectroscopic data, e.g.,infra-red and mass spectroscopic data, can be obtained on GC purematerials;

3. Columns conditioned employing the unit described in the presentinvention ameliorates the results of temperature and flow programmed gaschromatographic analyses;

4. Saves the time of very expensive and highly sophisticated instrumentsthat are otherwise occupied for conditioning columns;

5. Eliminates base line drift during programmed GC- analyses thusimproving integration accuracy;

6. The unit can be used for simultaneous conditioning of packed as wellas capillary columns of every conceivable shape such as straight,coiled, hairpin, pancake, helical, etc.

7. Individual column back pressure can be measured during columnconditioning by operating a selected valve switch. This not only enablesthe analyst later to i choose the optimum flow settings on aconventional gas chromatograph but also with minimum effort to check thesimilarity of two columns packed with the same uncoated or coatedsupport;

8. Eliminates the contamination of detectors with the lower molecularweight fragments normally present in the stationary liquid phases thatwould elute off of the wide bore packed and wall coated capillarycolumns during conditioning. Constant deposition of such impurities onthe detector components would have an adverse effect upon thesensitivity of such detectors, viz., thermal conductivity, flameionization, electron capt ure;and micro-cross section detectors.

COMPARATIVE ANALYTICAL DATA ON THE PERFORMANCE OF COLUMNS PREPAREDACCORDING TO THE PRESENT INVENTION AND THE KNOWN ART PRESENT INVENTIONKNOWN ART 1' K R 1",, K R

alpha-pinene 16.25 54.0 8.75 42.5

beta-pinene 27.50 79.0 3.0 12.50 75.0 1.6

myrcene 31.25 104.0 1.5 17.50 87.5 0.6

limonene 43.75 145.8 3.3 22.50 112.5 1.3 gamma-terpinene 55.00 183.3 3.628.75 139.5 1.5

COMPARATIVE ANALYTICAL DATA ON THE PERFORMANCE OF COLUMNS PREPAREDACCORDING TO THE PRESENT INVENTION AND THE KNOWN l' =Adjusted retentiondistance (mm) k=Parlition ratio R=The resolution of two adjacent peaksHETP=Height Equivalent to Theoretical Plates PROCEDURE FOR CLEANING ANDCOATING CAPILLARY TUBES The following procedure is employed for cleaningand coating capillary tubes, e.g., a stainless steel tubing having0.0625-inch external diameter and 0.02 inch internal diameter and 250feet long. It is highly useful in the GC-MS analysis of very complexmixtures of organic compounds such as essential oils and flavors.

In order to clean the capillary tube, one end thereof is connected toconduit 205 and the other end of the capillary tube is closed with asuitable plug. The means shown in FIG. 4 is fully assembled with diptube 195 in place. Conduit 207 shown in FIG. 1A is connected at 202 andthe other end thereof is dipped well below the cleaning fluid level incontainer 210 shown in FIG. 1A. Spigot 197 is connected to vacuumsource, e.g., by means of a suitable connecting conduit communicatingbetween 197 and port 43. Valve 54F is opened after the vacuum pump 70 isturned on and all other valves are closed. When the desired amount ofcleaning fluid has been transferred into 192 the vacuum is shut off.Spigot 197 is disconnected from the vacuum conduit and plugged bysuitable means. Dip-tube 195 prevents contact of the various surfaces oftee conduitl96 with highly corrosive cleaning fluids and, of course,make disassembly of the cylinder safer for the analyst or technician.

After cleaning fluid has been transferred into 192, dip tube 195 isremoved from the top of tee conduit 196 by unscrewing nut 199. One endof conduit 212 is then connected to threads 198 and the other end isconnected to high pressure gas supply port 142. The plug employed toclose off the outlet end of the capillary column is removed and aftermaking sure all other valves are closed, valves 5F and 307F are opened.The pressure on gauge 151F is adjusted to the desired level dependingupon the length and internal diameter of the capillary "tube, nature ofcleahin g solution, etc., e.g.,

between 100-400 psi such that the flow of nitrogen gas forces solutiondownwardly from cylinder 192 through the capillary tube. To disrupt theoperation at any instant close valve 307F and open valve 3011 This procedure may be repeated as many times as is required to effect cleaningof the capillary tube.

Coating capillary tubes can be accomplished by the same procedure andmeans hereinabove described except that a suitable coating solution issubstituted for the cleaning solution. It is also preferred to employ asmaller cylinder, e.g., as represented by cylinder 220. shown in FIG. 1.While the larger cylinder 192 can be employed for cleaning the capillarytubes, a cylinder of the same design as described with reference to FIG.4 but having a volume of 10-100 cc is most desirable for performingcoating operation.

In the coating procedure a pressure of 50-1 10 psi, for example, asindicated on gauge 151F is preferred depending upon the physicalcharacteristics of the coating solution and dimensions of the tube to becoated. It is also desirable to continue the flow of nitrogen throughthe capillary tube at a pressure, e.g., 50 psi, for 12 to 24 hours afterthe desired quantity of coating solution has been passed through thecleaned capillary tube. 1 A procedure for dynamic coating of capillarytubes is described in Dijkstra, G., and J DeGoey, Gas Chmmatography1958, D. H. Desty, Editor, Butterworths, London, 1958, p 56. Accordingto this method a suitable stationary phase is dissolved in a solvent andthen passed through the capillary tube. The deposition of stationaryphase material on the walls of the capillary tube is governed, amongother factors, by the rate of flow of solution through the tube,concentration of stationary phase and other factors related to specificcompositions.

The present invention provides means for eliminating physical variablesrelative to the coating procedure and thereby achieving morereproducible results as well as more efficient preparation of capillarytubes.

Having thus described the invention with reference to specificembodiments thereof many modifications and alterations thereof willbecome apparent to those skilled in the art without departing from thespirit and scope thereof.

I claim:

l. A system useful for the preparation of gas chromatography columns andtubes which comprises in combination:

a. first conduit means for passing inert gas from a second port means toa first port means, said first port means adapted for connection to anextrinsic coating and drying column, said second port means adapted forconnection to an extrinsic gas supply means;

b. valve means, and means for heating gas passed through said firstconduit means associated with said first conduit means;

c. second conduit means communicating with said first conduit means forpassing inert gas from said second port means to a third port means,said second conduit means containing valve means, said third port meansadapted for connection to an extrinsic packing column;v

d. and gauge means communicating with said first and second conduitmeans for indicating gas pressure therein.

2. The system of claim 1 containing vacuum producing means adapted forcommunication with said first port means.

3. The system of claim 2 containing third conduit means associated withsaid first conduit means for passing fluid from said first port means toa fourth port means, said fourth port means adapted for connection tosaid vacuum producing means.

4. The system of claim 1 containg means for indicating gas flow ratecommunicating with fifth port means through fourth conduit means, saidfifth port means adapted for connection to one end of a gaschromatography column.

5. The system of claim 1 containing sixth port means in communicationwith said fourth port means through fifth conduit means and said thirdconduit means, said sixth port means adapted for connection to saidextrinsic packing column.

6. The system of claim 1 in which said second port means communicateswith seventh port means through sixth conduit means and first conduitmeans, said sixth conduit means containing valve means and pressuregauge means.

7. The system of claim 1 being contained in suitable housing means.

8. The system of claim 7 in which vibrator means for assisting inpacking gas-liquid columns are attached to the outside of said housing.

9. The system of claim 7 in which said housing means is adapted withclamping means to hold in place extrinsic column means employed duringoperation of the system.

110. The system of claim 1 containing seventh conduit meanscommunicating between. said first conduit means and eighth port means.

11. The system of claim 1 in which said first conduit means containsfilter means.

1. A system useful for the preparation of gas chromatography columns andtubes which comprises in combination: a. first conduit means for passinginert gas from a second port means to a first port means, said firstport means adapted for connection to an extrinsic coating and dryingcolumn, said second port means adapted for connection to an extrinsicgas supply means; b. valve means, and means for heating gas passedthrough said first conduit means associated with said first conduitmeans; c. second conduit means communicating with said first conduitmeans for passing inert gas from said second port means to a third portmeans, said second conduit means containing valve means, said third portmeans adapted for connection to an extrinsic packing column; d. andgauge means communicating with said first and second conduit means forindicating gas pressure therein.
 2. The system of claim 1 containingvacuum producing means adapted for communication with said first portmeans.
 3. The system of claim 2 containing third conduit meansassociated with said first conduit means for passing fluid from saidfirst port means to a fourth port means, said fourth port means adaptedfor connection to said vacuum producing means.
 4. The system of claim 1containg means for indicating gas flow rate communicating with fifthport means through fourth conduit means, said fifth port means adaptedfor connection to one end of a gas chromatography column.
 5. The systemof claim 1 containing sixth port means in communication with said fourthport means through fifth conduit means and said third conduit means,said sixth port means adapted for connection to said extrinsic packingcolumn.
 6. The system of claim 1 in which said second port meanscommunicates with seventh port means through sixth conduit means andfirst conduit means, said sixth conduit means containing valve means andpressure gauge means.
 7. The system of claim 1 being contained insuitable housing means.
 8. The system of claim 7 in which vibrator meansfor assisting in packing gas-liquid columns are attached to the outsideof said housing.
 9. The system of claim 7 in which said housing means isadapted with clamping means to hold in place extrinsic column meansemployed during operation of the system.
 10. The system of claim 1containing seventh conduit means communicating between said firstconduit means and eighth port means.
 11. The system of claim 1 in whichsaid first conduit means contains filter means.